Furnace for smelting aluminium



Aug. 29, 1933. J. scHUFFLER 1,924,200

FURNACE FOR SMELTNG ALUMINIUM Filed DSC. 50, 1931 UNITED sTATI-:sJPATENT OFFICE FURNACE FOR SMELTING ALUMINIUM Julius Schler, Essen-Ruin', Germany, as-

sig-nor, by mesne assignments,` to The Koppers Company of Delaware, Pittsburgh, Pa., a Corporation of Delaware Application December 30, 1931, Serial No. 583,873, and in Germany january 5, 1931 l 11 Claims. (Cl. 26S-33) This invention relates to the smelting of aluthen passing the substantially cooled waste gases minium, aluminium alloys and other light metals over the molten metal, the quantity of waste of similar characteristics in gas-heated furnaces, gases and the period of their contact with the and more particularly to gas-heated smelting cold solid metal being so adjusted that the liquid furnaces of the type which are provided with metal is brought exactly tothe smelting tem- 60 a chamber for preheating the metal'entering into perature desired. the smelting chamber or hearth of the furnace. Preferably I do not bring the hot waste gases In the known metal smelting furnaces of the issuing from the gas burner directly into contact type referred to, as used for instance for smeltwith the cold metal; I pass them iirst from outing copper, brass and similar heavy metal alloys, side against the Wens 0f the Preheatng eheln- 65 the hot gases issuing from the gas burner are ber, so' that I rst heat the cold metal indirectly rst passed over the liquid metal and then and only bring the hot Waste gases into contact brought into contact with the cold metal which with the solid metal for the purpose 0f melting has been introduced into the preheating chamber it When they have Cooled t0 a medium temof the furnace. In accordance with the path peratue, after Which I Dass the gases OVeI the 70 of the gases relative to the path of the metal m0115611 metal. in the hearth, this Itype of heating may be re- A further object of my invention is to provide ferred to as counter-current heating. an mplOVed gas-heated smetng furnace t0 Del- For smelting aluminium, aluminium alloys and mit 0f Carrying Out the Inethed 0f smelting other light metals of similar characteristics,the according to the invention.

method above described is extraordinarily dis- The Smeltine furnace according to the invenadvantageous, lin so far as the high degree of tOn possesses, beside O1` abOVe thevat 0I' trough latent heat of fusion of the light metals renders which receives the molten metal, a Chamber for Y it practically impossible to avoid heating the Preheating tneleod metal. in the adjaeeney 0f liquid metal bath above the optimum casting Which gas burners are disDOSed Whose Waste 39 temperature. Apart from the increased oxidagases are lst used OI preheating the metal tion which involves :considerable loss of metal Y contained in the Dreheatng Chamber Tand are any superheating leads to a very considerable then passed over the molten metal contained in absorption of gas in the metal. The gas dissolved the smeltng trOugh.

in the liquid metal at high temperatures only In the furnace according to the invention the g5 escapes very slowly from-the metal when the preheating chamber consists preferably of one latter cools down and solidies. Consequently 0r more mufes heated eXternelly by burners and the cast blocks formed of superheated metal usuflowed over by the hot gases. These muffles open ally contain a number or more or less large gas into the smelting trough which is also connected v bubbles which make it impossible to form comwith the gasflues or channels provided on the 90 pact homogeneous plates from such blocks. outside of the mulfles, so that after giving up the The special properties of aluminium, alumingreater part of their heat to theTl walls of the ium alloys and other light metals of similar namuiiies and the adjacent brickwork of the furture render the employment of the smelting furnace, the hot gases can be lpassed over the liquid 4o naces ordinarily used for dealing with copper, metal before flowing away into the gas dis- 95 brass and other metals quite irrational for smeltcharge nue emerging from the smelting trough. ing light metals. Light metals have quite dif- The improvements in the smelting of aluminferent physical characteristics from the heavy ium, aluminium alloys and other light metalsmetals, a fact which hitherto has been often of similar nature which are herein set forth take overlooked in the construction of furnaces for account above all of the fact that a very consid- 100 smelting light metals.' verable amount of heat must be supplied to the One object of present invention is to prosolid metal for the purpose of converting it into vldeamethod of smelting aliairriii'iium', aluminium. the liquid state', whereas the vamount of heat alloys and other light 4me'ta'al'slf of similar charrequired for keeping the molten -metal in the 5o acteristics which will enable 'thesaid light metals liquid state is relatively small. Moreover in the 105 to be correctly smeltedin'l acor'dance "with Athe furnace according to the invention the gases do physical properties of thesemmetals". -not 'come into contact wlththe molten metal d1- l The method devised'byin'ie fconsists in first rectly they have left the burner', i. e. with their using the h ot gase'sfdevelopd Aby a gas burner-'- highest temperature, but only act either directly for Vprelleatingt under' treatment and or indirectly on the vcold solid metal to which 110 ter.

By means of the present invention in smelting aluminium, aluminium alloys and other light metals of similar characteristics a reduction in oxidation losses and in the absorption of gas in the liquid metal is obtained, While at the sa-me time ahigh thermal efficiency of the furnace is -obtained. The latter point is due to the fact that the burners used for heating the furnaces can be allowed to work up to a very high temperature. Y

A further important feature of the aluminium smelting furnace invented-by me consists in the fact that the floor of the preheating muiile is extended so far in the direction of the smelting troughA thatthe waste gases entering into the smelting trough over the upper edge of the muille meet the, upper-part of the solid metal blocks which are situated at the exit of the muflie. Con-v sequentlvl the heat contained in the waste gases is utilized directly for converting the metal into the liquid state without possibly being able to cause the liquid metal to become superheated.

The nal object of my invention is to provide an improved construction of smelting furnace for carrying out the method according to theinvention. y

According to my inventionI arrange the smelt-` ing trough and the' preheating muifles in an approximatelyl cylindrical housing adapted to pivot about its longitudinal axis, the preheating muffles being disposed at the end faces of the housing. This` construction permits the smelting trough to be relatively long, which is advantageous in so far as the heating gases thereby remain in contact with the liquid metal for a relatively long period of time, which as is obvious enables the heat of the heating. gases to be utilized fully.

I also'prefer to provide in the roof of the fur-` nace above the smelting trough one or more auxiliary burners for heating the liquid metal directly. Theseauxiliary burners may be shut. olf from the smelting trough by means of slide l valves. e e

The provision of auxiliary burners is of advantage because it enables the liquid metal contained in the smelting trough to be kept in thev liquid condition even when the heating of the muilles is arrested, and also enables the metal inthe trough to be quickly reheated if it should fall below the desired temperature.

With these and other objects of my invention in view I willnow describe the nature of the invention on the lines of the accompanying drawing in which:-

`Figure 1v is a vertical longitudinal section through a" gas-heated light metal smelting furnace constructed in accordance with the invention,

Figure 2 is a cross-section along the line 2-2 of Figure 1 and Figure 3 is a vertical cross-section along the line 3-3 of Figure 1. y

The furnace illustrated in the drawing con'- sists of an approximately semi-cylindrical metal' housing 1 lined with a material 2 which is a bad 'conductor of heat, on which the refractory material, preferably a ceramic material such as sillimanite or the like which is relatively inassailable bg light metal is disposed which is used fer forming the smelting trough and the heating arrangea spout 5. The opening 6 can be closed by means v of a slide valve 6a secured by means of a chain 6b to a lever arm 6d having a counter-weight 6c. The two end walls of the metal trough 4 are bevelled off at 7 or 7a. At the upperend of each of the bevels a muille 8 composed of 'a highly refractory material. such as sillimanitefopens into the trough 4, the muiiles being accessible from' outside through tubular charging chambers 9' secured to the end walls of the furnace.

The preheating muflles 8 are heated from outside by means of burners 10 disposed tangentially to the muilles. The waste gases from these burners circulate round the muliles through the flues 1l and 12 which are connected together by means of openings 13.

The waste gases flow from the flues 12 throug an opening 13 provided between the upper edge 14 of the mule and the furnace roof into the trough 4, being so diverted by means of an inclined surface 16 of a throat extending to the furnace roof that they impinge partially against the part of the solid metal 17a lying on an extension 1'7 of the mulle bottom.

A portion of the gases is Withdrawn from the trough through the flues 18, but most of it flows over the molten metal in order to keep the latter at the desired casting temperature, and is then withdrawn through the central ues 19 into longitudinal ues 20 provided in the sides of the furnace. 'In one of these longitudinal flues a metalpipe 21 is disposed, through which the cold air for combustion is passed from without in `or der to be preheated. The heating gases are preferably withdrawn through a chimney attachment 22 provided in the furnace roof. The discharge nues of the furnace can however also be connected with a flue disposed axially to the end face of the furnace, to lead the gases to a chimney lying remote from the furnace.

In the middle of the furnace a series of burners 24 are provided in the roof 23, which can be shut off from the inerior of the furnace by means of slide valves 25 adjustable from without. These burners serve selectively, that is, according to the metal or alloy to be smelted and the temperature desired, to regulate the temperature of the liquid metal contained in the troughin order to avoid superheating the metal.

As stated the solid metal which is forinstance in the form of pigs 17a is charged into the furnace through the chambers 9 provided at the end faces of the furnace. The chambers 9 can be closed in the ordinary manner by means of vertically moving sliding doors 26 which are secured by means ofchains 2.7 to a segmental element 29-pro vided with a counterweight 28. The `usual observation holes are provided in the sliding doors.

Combustion air is fed to the `burners 10 and 24 cthrough pipes 45 which are connected tothe metal pipe 21 providedin the waste 'gas -ue 20. The

is attached at 47 by means of a flexiblepipee As 150 negated shotvn in the drawing, all the burners are pro=- vided with cccirs for regulating the supply oi air illustrated in the drawing is con= structed tip over in order to pour out the molten metal contained in the furnace.

rails 33 are provided on the lovver part of the housing tvb-ion rest on rollers 34 of the base plate threaded spindle 36 serves to rnove ment oi the nut.

lt finally be mentioned that it is of advanm tage to provide all the Waste gas ues leading .from the furnace with regulating valves in order permit the quantity of gases passing through each ci the :dues to be adapted to the existing conditions. l

rThe invention as hereinabove set forth is em-n hcdied in a particular form but may be variously erniodied within the scope of the claims hereinfs after made.

l claimzml. A. process for smelting aluminium, aluminium alloys or other light metals of similar characterisu tics, comprising bringing the hot gases formed by the combustion of a heating gasrst into con= tact with the outer Walls of a muifle consisting of refractory material in which the cold metal to be treated is contained then bringing the hot gases into Contact with the solid metal preheated in the munie, and finally bringing the hot gases into con= tact with the liquid metal formed by smelting the metal.

2. l furnace for smelting aluminium, alumin= iurn alloys or other light metal of similar characteristics, comprising a smelting trough, rgas discharge iiues starting from the space above, the same, a inutile for preheating the metal to be smelted so disposed near the smelting trough that the metal can now from the preheating mulile into the smelting trough, burners for the combusu tion oi a gas so disposed that the hot waste gases of same after coming into contact with the outer surfaces of the munie come first into contact with the solid metal contained in the preheating cham--I i her and are then passed over the liquid metal contained in the smelting trough. y

3. A furnace according to claim 2 wherein a number oi mufrles for preheating the metal to loe treated are provided, with. separate gas burners for each mufle chamber. y

4. A furnace for smelting aluminium, alumin= lum alloys or other light metals of similar char acteristics, comprising a. smeltingrtrough, gas discharge flues starting from a space above the same, a muie composed of refractory material disposed near the smelting trouglr and so ar-= ranged that the cold metal to be treated can be introduced therein, said muille so disposed relaa For this pur Y et tive to the sinelting trough that the metal can new from` the mtime into the smelting trough, burners ior the combustion of a gw so 'arranged that the hot Waste gases oi seme come nrst into contact with the outer surfaces oi the intime, then with the solid metal situated at the outlet of the munie and are finally passed over the liq`= uid metal contained in the smelting trough.

5. A furnace according to claim d wherein a number of munies are provided with separate gas burners for each noodle.

6. A. iurnace as set forth in claim al wherein the bottom-of the mudeis extended towards the smelting trough and openings are provided above this extension leading to the fluesvsurrounding the mufe, said openings so arranged that the hot gases flowing from the openings impinge against the metal lying on the extension of the iloor of the mame,

7. .A furnace as set forth in claim e wherein the `bottom of the preheating chamber or muille is inclined towards a smelting trough and termiL1 nates, on a level lwith the upper edge of the smelting trough.

8. .A furnace for smelting aluminium, saturninn1 iuni alloys or other light metals of similar characteristics comprising a 'sinelting trough, gas discharge nues starting from a space alcove the same, pipes arranged in the gas discharge hues for the passage of the cold combustion air for the purpose of preheating same, said pipes connected with the gas burners of the furnace, a muie chamber for the metal to be smelted so disposed near the srnelting trough that the metal can flow from the mule chamber into the smelting trough, burners for the combustion of a gas so disposed that the hot waste gases of 'same iirst come into contact with the outer surfaces of the munie, then the solid metal contained in the preheating chamber and are thereafter passed over the liquid metal contained in the smelting trough. l

9. A furnace for smelting aluminium, aluminn lum alloys or other light metals of similar charl acteristics, comprising an approximately cylindri cal housing rotatable about its longitudinal axis, a trough for receiving the molten metal disposed in the housing, the wall oi said trough provided with an opening through which the liquid metal can flow out when the furnace is rotated, a mule for preheating the solid metal provided at each of the side ends of the furnace, said mue surrounded on the outside by flues which open into the smelting trough above the end of the inutile, gas burners so disposed that the hot waste gases oi saine flow into the flues surroundingthe muie and waste gas flues emerging from the smeltlng trough.

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